US investigators have removed bags of evidence, including DNA samples, after searching the home where the widow of one of the Boston bomb suspects has been living.

The search came after female DNA was found on at least one of the bombs used in the attack which killed three people and injured more than 260 at the Boston Marathon.

On Monday, officers visited the Rhode Island home of the parents of Katherine Russell, the wife of Tamerlan Tsarnaev, where Ms Russell has been staying since her husband was killed in a police shootout after the attack.